Production of homolgues of aniline



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Patented Feb. 9, 1932 UNITED STATES PATENT OFFICE WESLEY MINNIS, F BUFFALO, NEW YORK, ASSIGNOR TO NATIONAL ANILINE &; CHEMICAL COMPANY, INC., OF NEW YORK, N. Y., A. CORPORATION OF NEW YORK PRODUCTION OF HOMOLOGUES OF ANILINE No Drawing.

This invention relates to a process for the production of homologues of aniline, more particularly to the production of aminotrimethylbenzene, and includes correlated improvem-ents and discoveries whereby and wherewith the production of such compounds is enhanced.

An object of the invention is to provide a process for the production of homologues of aniline by heating a hydrolu'omide or hydroiodide ot' a N-alkylated homologue of aniline at atmospheric pressure.

Another object of the invention is to provide a process for the production of homologues of aniline which shall be more simple than the processes heretofore utilized and which maybe practiced on a con'uuercial scale with efficiency and facility.

Further objects of the invention are to provide a process for the production of homolog'ues of aniline in accordance with which the cost of production is lowered through. the utilization of less expensive equipment and in which the operating hazard is reduced through the elimination of the use of high pressure vessels as autoclaves.

ther objects of the invention will in part be obvious and will in part appear hereinutter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, which will he exemplified in the process hereinafter disclosed, and the scope of the application of which will be indicated in the claims.

Toluidine was prepared by Hotlimann by heating N-1nethylauiline hydrochloride or N-methylaniline hydroiodide under pressure in a. closed tube (Ber. 5, 7Q0l872-). Other reactions of this type have been investigated by a number of experimenters, who also worked with pressure apparatus. The prevailing theory appears to he that outlined by Michael Ber. 11;, 2l0T-1881-), namely, that the formation of toluidine hydrohalide from N-methylaniline hydrohalide takes place through the dissociation of the salt into aniline and methyl halide followed by the halide attackin the replaceable hydrogen in Application filed November 13, 1829. Serial No. 407,005.

at atmospheric pressure due to the removal or escape of the products of dissociation from the field of action because of their volatility at the temperature of rearrangement. In the case of the hydrochlorides of the N-methylarylamines, this theory appears to be borne out by practice.

In the practice of the present invention, when an alkylarylammonium bromide or an alkylarylammonium iodide of the benzene series, particularly an N-monomethylated homologue of aniline, is heated at atmospheric pressure, there is produced, in excellent yields, the hydrobromide or hydroiodide of a higher homologue of the respective aromatic amine, which homologue has a lesser number of alkyl substituents in the amino group.

By operating at atmospheric pressure, a distinct advantage is secured, because the hazard of operating under hi gh pressure with a corrosive material is eliminated. Moreover, it is possible to use less expensive equipment in place of the autoclaves heretofore employed.

The temperature at which to accomplish the rearrangement depends among other factors, upon the particular compound being treated. In general, the rearrangement occurs above about 230 C. The speed of reaction is greater between about 250 and 290 (3., and in some cases, the temperature may be raised to 350 (l. or higher. According to the present invention, the hydrobromide or the hydroiodide of an N-alkylated arylamine, such as methyl, ethyl, propyl, butyl, etc., is heated at a temperature of about 230 to 350 (1, or higher in an open vessel for several hours, or until rearrangement is substantially complete. If the compound, or compounds, undergoing treatment have a boiling point within this temperature range, it may be advantageous to use an open vessel in conjunction with a reflux. condenser to prevent loss. The reaction mixture is then treated with an alkali in known manner to liberate the free amine, which latter may be following examples are presented. The parts are by weight.

Example 1.-12 l.5 parts of N-monomethyl-otoluidine hydroiodide are charged into a'kettle equipped with an agitator and a reflux condenser, and are heated to'boiling, or about 230 C. As the rearrangement proceeds the boiling point rises, and the temperature of the mass rises to about 260 C. over a period of 5 hours. The reaction mass is permitted to cool somewhat and is then run into 101 parts of a well agitated 20 per cent. caustic soda solution. Agitation is discontinued and the mixture permitted to stratify, after which the upper oily layer is drawn oil. It contains asymmetrical m-xylidine in admixture with other products of the reaction, which may be separated in any suitable manner.

E sample 2.700 parts of a mixture of N- methylxylidines (prepared by 'monomethylating technical mixed xylidines and containingabout 48 per cent. secondary amines) are charged into a kettle equipped with an agitator, and 920 parts of aqueous hydrobromic acid, containing 48 per cent. hydrogen bromide, are added with agitation; As the temperature is raised, first water, and then unreacted hydrobromic acid distills off until the mass becomes substantially anhydrous.

When the temperature reaches about 245to 250 C., the anhydrous mass begins to boil. The vapors evolved are returned to the reaction kettle by a reflux condenser. The temperature is maintained at 250 to 265 C. for about 4 hours or until the rearrangement is substantially complete, and is then permitted to drop to about 175 C. whereupon the mass is introduced into 1100 parts of a well agitated 20 per cent. solutionof caustic soda. The mixture is heated to nearly boiling, agitation is discontinued and the liquid is permitted to stratify. The upper oily layer which contains a mixture of the isomeric amino trimethylbenzenes is separated, washed with water and distilled. 1

E wam-ple 3.67 .5 parts of mixed isomeric N-monomethylxylidines, containing about 98 per cent. secondary amines, are treated with about 88 parts hydrobromic acid solution containing about 48 per cent hydrogen bromide. The mass is heated whereupon water and unreacted hydrobromic acid are distilled oif, and the anhydrous mass further heated under'a reflux for about-8 hours. The tem perature is then-permitted to drop and the fluid mass is run into 105 parts of a well agitated 20 per cent. caustic soda solution. Agi tat-ion is discontinued, and the liquid is permitted to stratify. to the top comprises a crude mixtureofthe benzene The liquid which rises I isomeric aminotrimethylbenzenes. These may be recovered in any suitable manner.

E sample l.-268 parts of N-monoethylparaxylidine hydroiodide (prepared by ethylating technical para-xylidine by means of ethyl iodide) are charged into akettle equipped with an agitator and a reflux condenser. The charge is heated to about 270 to 275 C. under reflux for about 8 hours. The charge is then cooled to about-150 to 175 (1., and the fluid mass is added to 200 parts of a wcllstirred20 per cent. solution of caustic soda. Stirring is discontinued, themass permitted to stratify, and the upper layer, which comprises crude aminodimethylethylbenzene, is separated and, if desired, pur'ifiedi V In the aboveexamples in placeof the hydrobromide, the equivalent amount of the hydroiodide of the corresponding alkylarylamines may be employed.

The temperature at which rearrangement occurs is generally at'or near the boiling point of the alkylarylammonium salt. In general, those temperatures lie between 230 and 300 C. Th'etime required to effect-rearrangement willdepend in part on the temperature at which the rearrangement'is conducted, inasmuch'as the higher temperatures tend to increase the speed of reaction.

It will be underst0od,'of course,that the invention is not limited tothe rearrangement of secondary amines, nor to the production of primary amines. By operating on the hydrobromid'e or hydroiodide of an N-dialkylarylamine or quaternary trialkylaryl ammonium bases of the benzene series, the corresponding primary, secondary or tertiary homologues, or mixtures-thereofmay be produced, depending upon the temperature at which the heating occurs and the'time of heating. The homologues produced-will have a correspondingly lesser number of alkyl substituents in the amino group. Thus, for example, in heating trimcthyltolylammonium bromide, there may be produceda mixture comprising dimethylxylidine hydrobromide, methylaminotrimethylhydrobromide and aminotetramethylbenzene hydrobromide, which may be separated in any convenient manner. Also,

mixtures 'of the hyd'robromic-or hydroiodic acid salts of primary and dimethylated amines, for example, a mixture of the hydrobromide of xylidine and of dimethylxylidine may be used for the production of aminotr'imethylbenzene.

' Since certain changes in carrying out the above process may be made Without departing from its scope, it is intended that all matter contained in-- the above description shall be interpreted as illustrative and not in a limiting sense.

I claim: 1, .A process for the production of homologues of aniline which comprises heating one of the group consisting of alkylarylammonium bromides and iodides oi the benzene series at a temperature of about 230 to about 350 C. at susbtantially atmospheric pressure.

2. A process for the production of homologues ot' aniline which comprises heating one of the group consisting of hydrobromides and hydroiodides of N-alkylated homologues of aniline at a temperature of about 230 to about 350 C. at substantially atmospheric pressure.

3. A process for the production of homologues of aniline which comprises heating one of the group consisting of hydrobromides and hydroiodides of N-alkylated aminomethylbenzenes at a temperature of about 230 to about 350 (3., at substantially atmospheric pressure.

a. A process for the production of homologues of aniline which comprises heating a hydrobromide of N-alkylated aminomethylbenzenes at a temperature of about 230 to about 350 C. at substantially atmospheric pressure.

5. A process for the production of homologues of aniline which comprises heating one of the group consisting of hydrobromides and hydroiodides, of N-alkylated Kylidines at a temperature of about 230 to about 290 C. at susbtantially atmospheric pressure.

6. A process for the production of homologues of aniline which comprises heating a hydrobromide of an N-alkylated xylidine at a temperature of about 230 to about 290 C. at substantially atmospheric pressure.

7. A process for the production of ho1nol logues of aniline which comprises heating one of the group consisting of methylarylammonium bromides and iodides of the benzene series at a temperature of about 230 to about 300 C. at substantially atmospheric pressure.

one of the group consisting of hydrobromides and hydroiodides of N-methylated aminomethylbenzenes at a temperature of about 230 to about 300 C. at substantially atmos pheric pressure.

10. A process for the production of homo logues of aniline which comprises heating a by drobromide of N-methylated aminomethylbenzenes at a temperature of about 230 to about 300 C. at substantially atmospheric pressure.

11. A process for the production of homologues of aniline which comprisesheating one of the group consisting of hydrobromides and hydroiodides of N-methylated xylidines at a temperature of about 230 to about 290 C. at substantially atmospheric pressure.

12. A process for the production of homologues of aniline which comprises heating a hydrobromide of an N-methylated xylidine at a temperature of about 230 to about 290 C. at substantially atmospheric pressure.

13. A process for the production of homologues of aniline which comprises heating a hydrobromide of an N-monomethylxylidine at a temperature of about 245 to about 265 C. at substantially atmospheric pressure.

14. A process for the production of homologues of aniline which comprises heating a hydrobromide of a mixture of N-monomethyl- Xylidines at a temperature of about 245 to about 265 C. at substantially atmospheric pressure.

15. A process for the production of homologues of aniline which comprises admixing N-methylxylidines with a solution of hydrobromic acid, heating until the admixture becomes substantially anhydrous, maintaining the temperature at about 245 to about 265 C. until rearrangement is complete, introducing into caustic soda solution and separating the aminotrimethylbenzenes.

16. A process for the production of homologues of aniline which comprises admixing N-methylxylidines with an aqueous solution of hydrobromic acid containing about 48 per cent. hydrogen bromide, heating until the admixture becomes substantially anhydrous, maintaining the temperature at about 245 to about 265 C. under a reflux for about 4 hours, introducing into a well agitated 20 per cent. aqueous caustic soda solution, allowing the liquid to stratify and separating the aminotrimethylbenzene.

WESLEY MINNIS. 

